Can you share the content of your 000-default.conf file and the details of the syntax error that was displayed. With that information it’ll be much easier to help you identify the issue.

000-default.conf

<VirtualHost *:80>
        ServerName example.com
        Redirect permanent / example.com
</VirtualHost>
<VirtualHost *:443>
        ServerAdmin webmaster@localhost
        DocumentRoot /var/www/html
        ServerName example.com
        Header always set Strict-Transport-Security "max-age=63072000; includeSubDomains;"
        SSLEngine on
        SSLProtocol All -SSLv2 -SSLv3
        SSLCipherSuite EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH
        SSLHonorCipherOrder On
        Header always set X-Frame-Options DENY
        Header always set X-Content-Type-Options nosniff
        SSLCertificateFile /root/ssl/example.com.crt
        SSLCertificateKeyFile /root/example.com.key
        SSLCACertificateFile /root/ssl/intermediate.crt
        SSLUseStapling on

        <Directory /var/www/html/>
            Options Indexes FollowSymLinks
            AllowOverride All
            Require all granted
        </Directory>

        ErrorLog ${APACHE_LOG_DIR}/error.log
        CustomLog ${APACHE_LOG_DIR}/access.log combined
</VirtualHost>

Error messages:

Action 'start' failed. The Apache error log may have more information.

A few errors that I picked up on the Apache error log/var/log/apache2/access.log:

[Tue Aug 23 10:58:31.630380 2016] [ssl:emerg] [pid 12152] AH01958: SSLStapling: no stapling cache available

[Tue Aug 23 10:58:31.630447 2016] [ssl:emerg] [pid 12152] AH02311: Fatal error initialising mod_ssl, exiting. See /var/log/apache2/error.log for more information